The present invention relates generally to hypodermic syringes and, more particularly, to a hypodermic syringe having a plunger which separates from a piston in a barrel of the syringe after a downward stroke of the plunger preventing further use of the syringe.
The increase in infectious diseases such as AIDS, hepatitis, etc., and the use of syringes by drug users have led to increased incidents of blood-borne diseases resulting from the reuse or sharing of syringes. One way of alleviating this problem is by providing syringes that may be used only one time. If a syringe breaks or is self-destroying when used a first or single time, then the syringe becomes useless after a single injection and will have to be discarded preventing reuse of the syringe. It would be desirable for such a single use syringe to be easy to use and relatively inexpensive to manufacture.
In the past, a number of disposable syringes have been proposed. For example, disposable syringes having rods, pins, knives or cutting edges used to puncture or cut the barrels or other parts of the syringes upon first use of the syringes are disclosed in U.S. Pat. Nos. 4,687,467, issued to Cygielski on Aug. 18, 1987; 4,391,273, issued to Chiquiar-Arias on July 5, 1983; 3,998,224, issued to Chiquiar-Arias on Dec. 21, 1976; 3,951,146 issued to Chiquiar-Arias on Apr. 20, 1976; and 3,667,657, issued to Chiquiar-Arias on June 6, 1972; and French Patent No. 2,298,340 to Blanie, dated Aug. 20, 1976. However, these types of syringes may present problems because the syringes will leak if users attempt to reuse the syringes after they are cut or punctured. Also, when a syringe is punctured by pushing a pin or rod through the forward portion of the syringe barrel, it may be possible to avoid damage to the syringe and allow reuse of the syringe by not pushing the syringe plunger all the way to the front of the barrel.
Some syringes may be reused even though they were intended to be used as disposable or non-reusable syringes. For example, U.S. Pat. Nos. 4,675,005, issued to DeLuccia on June 23, 1987, and 4,026,287, issued to Haller on May 31, 1977, disclose syringes having a piston that engages a forward needle-supporting portion of the syringe pulling the portion free of the syringe barrel toward the back of the syringe upon withdrawal of the syringe plunger. Nevertheless, this type of syringe may be reused by simply not pushing the piston all the way to the front of the syringe, thereby avoiding engagement with the forward needle-supporting portion. U.S. Pat. No. 4,650,468, issued to Jennings Jr. on Mar. 17, 1987, describes a syringe having a plunger that may be used to retract a forward needle-supporting portion toward the back of the syringe where it may be locked in place preventing reuse of the syringe by moving the plunger forward for an injection until it engages the needle-supporting portion and then rotating the plunger until the portion separates from the barrel of the syringe, allowing the portion to be pulled to the back of the syringe. This type of syringe may be reused by not rotating the plunger after each injection.
U.S. Pat. No. 3,478,937, issued to Solowey on Nov. 18, 1969, shows a syringe that has a disc attached near the rear of a plunger that is locked to the back of the syringe, making the syringe inoperable, by pushing a piston attached to the front of the plunger toward the front of the syringe. Once again, this type of syringe may be reused by simply not pushing the piston all the way to the front of the syringe preventing the disc from locking to the rear of the syringe. A piston attached to a plunger in U.S. Pat. No. 4,233,975, issued to Yerman on Nov. 18, 1980, is pushed forward until it forces a plugging member to block the needle passageway at the front of the syringe, preventing fluid from exiting the syringe. This syringe may be reused by pushing the piston only part of the way forward so that the passageway is not blocked.
Syringes having a piston that is locked to the front of the syringe barrel when a plunger is pushed forward for an injection are described in U.S. Pat. Nos. 4,713,056, issued to Butterfield on Dec. 15, 1987, and 4,391,272, issued to Staempfli on July 5, 1983. A person may reuse this type of syringe by not pushing the plunger all the way forward, preventing the piston from being locked to the syringe barrel.
Non-reusable syringes prefilled with medicinal fluid to be injected into a patient which have plungers that move in only one direction toward the front of the syringes are disclosed in U.S. Pat. Nos. 4,493,703, issued to Butterfield on Jan. 15, 1985; 4,367,738, issued to Legendre, et al. on Jan. 11, 1983; and 4,252,118, issued to Richard, et al. on Feb. 24, 1981. None of the syringes described in these three patents have a plunger which may be retracted toward the rear of a syringe for the purpose of filling the barrel of the syringe with the medicinal fluid needed for an injection. As a result, all of these syringes must be prefilled with needed medicinal fluid and can only be used to inject one type of prefilled fluid. Unlike the above three syringes, a syringe having a plunger that can be withdrawn for the purpose of filling or loading the syringe can be used to inject any type of medicinal fluid. U.S. Pat. No. 4,252,118, issued to Richard et al. on Feb. 24, 1981, describes a syringe having a plunger which detachably engages a piston. A slight rearward pressure may be applied to the plunger shown in this patent to draw some fluid from a patient in order to perform a "vein test" to make sure that the needle is not improperly placed in the patient, but the plunger cannot be withdrawn for the purpose of filling or loading the syringe with medicinal fluid needed for an injection without disconnecting the plunger from the piston.
A syringe having a connector, attached to a piston, which engages a Z-shaped guide groove in a plunger inside a barrel of the syringe is disclosed in U.S. Pat. No. 4,699,614, issued to Glazier on Oct. 13, 1987. The syringe may be filled with medicinal fluid by withdrawing the plunger toward the back of the syringe. The piston and connector disengage from the Z-shaped guide groove in the plunger following an injection of the fluid from the syringe. However, the syringe is not destroyed after a single use and it may be possible to engage the connector to the Z-shape guide groove in the plunger for another use of the syringe if a user is willing to spend enough time and effort to accomplish this task. A second syringe design is shown in this patent which uses liquid adhesive contained in a cavity of a collar holder attached to a piston to cement together the parts of the syringe preventing reuse thereof after a plunger is withdrawn following an injection. The withdrawn plunger pulls a filament or cord attached to a cap covering the cavity causing the cap to pull free and the adhesive to spill into the barrel of the syringe. Nevertheless, this syringe may be reused by not retracting the plunger all the way back after an injection in order to prevent the cap from pulling free of the cavity.
Different non-reloadable syringe embodiments are described in U.S. Pat. No. 4,731,068, issued to Hesse on Mar. 15, 1988, which allow a plunger to go through one complete cycle of being withdrawn to load the syringe with medicinal fluid and then being pushed forward to inject the fluid. However, the designs of these embodiments are complicated and expensive and do not facilitate simple modifications of existing syringe designs. Another expensive and complicated syringe design is shown in U.S. Pat. No. 3,890,971, issued to Leeson, et al. on June 24, 1975. This syringe uses an ampule pre-filled with medicine and is not intended for use with different medicinal fluids.
Syringes that are reusable until the needles or other parts thereof are bent, broken or made inoperative are disclosed in U.S. Pat. Nos. 4,728,321, issued to Chen on Mar. 1, 1988 (needle cemented to cap); 4,710,170, issued to Habner, et al. on Dec. 1, 1987 (needle bent by plunger in barrel of syringe); 4,634,428, issued to Cuu on Jan. 6, 1987 (device in cover used to bend needle); 4,332,323, issued to Reenstierna on June 1, 1982 (projections in sleeve used to bend needle); 4,266,544, issued to Wardlaw on May 12, 1981 (device mounted at front of syringe used to bend needle); and 3,306,291, issued to Burke on Feb. 28, 1967 (lateral movement breaks boss portion of barrel of syringe).
Other syringes are disclosed in British Patent No. 1,150,980 to Husted-Andersen, dated May 7, 1969; and French Patent No. 1,500,009 to Auberlinder, dated Nov. 3, 1967.
Accordingly, there is a need for a single use hypodermic syringe having a plunger, engaged to a piston, which may be withdrawn to load the syringe with medicinal fluid, pushed forward to inject the fluid, and then retracted after the injecting causing the plunger to separate from the piston destroying the syringe and preventing reuse of the syringe. Such a syringe should be inexpensive to fabricate and easy to adapt to existing syringe designs.